I am British by my father, and Thai by my mother. I'm 44 years old. Are there restrictions on applying for Thai nationality that will require dropping my British nationality?

UK has no restrictions and there is no need to drop any nationality to claim your Thai by birth nationality.

you also don't apply for it.

You are already Thai. A child of a Thai parent is Thai automatically.

If you were born in Thailand, then your Thai birth certificate will be proof.

If born outside of Thailand, you need to have the Thai embassy in that country issue you with a Thai birth certificate, which will be proof.

From there, you can apply for a passport.

An off-topic post has been deleted.

"Brit/Thai Dual Nationality Half-caste by birth, obtaining Dual Nationality"

"Are there restrictions on applying for Thai nationality that will require dropping my British nationality?"

No, "Half-caste by birth", a very derogatory term in most quarters, are allowed passports by both countries.

Edited June 25, 201115 yr by TerryLH

Correct. Thai nationality by birth is acquired on the basis of the parents' nationality, ie at least one parent must be a Thai national. Racial origin plays no part. See Thailand's Nationality Act, sections 7–12 regarding the acquisition of Thai nationality.